As is known, the railway industry requires that the railbed ballast be tamped periodically in order to maintain or correct as required the alignment and elevation of the rails. Complex machines which ride on the rails and carry out the tamping operation as they move along have been developed and are widely used.
The tamping tools which are used on these machines and which actually do the tamping are subject to extreme conditions. The tools are plunged down into the crushed rock ballast and moved horizontally through the ballast, then withdrawn, while at the same time being subjected to a vibratory motion. It is the effect of these violent conditions on the tamping pad at the end of the tool and on the tool shank which gives rise to the present invention.
The tool generally takes the form of a shank which has integral foot at the end thereof and has attached to the foot a tamping pad or shoe. The tamping pad is generally attached to the shaft by bolts, welding or a combination of the two. The tool is therefore for practical purposes a one piece factory made unit. Once installed, the unit is utilized until the pad wears out or the shank breaks. The unit is then consigned to scrap. This is highly wasteful, since the shank will usually outlast the pad. Even if the shank breaks before the pad is worn out, there is a substantial waste factor in scrapping the combined unit since the pad normally represents something in the area of 20% of the value of the tool.
It would therefore be highly advantageous and cost efficient to have a two piece tamping tool in which the tamping pad and the shank can be separated without difficulty in the event of the failure of one of them, so that only the failed part need be replaced. As a general proposition, the railways would find it very advantageous to be able to install and use a single set of shanks for an entire tamping season, replacing only the pads as required.
To date no satisfactory system utilizing readily removable pads has been made available.
Against this background the present invention provides a two piece tamping tool which permits the tamping pad to be readily removed from the shank. The invention also extends to the shank and the tamping pad per se, and to a method of joining the two.